Traditional methods of pearl oyster cultivation tend to be inefficient. For example, there is no guarantee that each oyster that is cultivated would produce a pearl at all, let alone a pearl possessing a desired characteristic. A pearl is produced through about 1 to 3 years of cultivation of the pearl oyster following transplantation into the pearl oyster gonad of a nucleus made of, for example, a piece of a shell, along with a piece of mantle tissue. Many factors combine to vary the results of pearl oyster cultivation, and consequently usually only a portion of the pearl crop is of acceptable quality. For example, an oyster may get weak from overcrowding or a lack of sufficient plankton in the water in which it is being cultivated. Hitherto, conditions agreeable for a pearl oyster with respect to pearl formation are generally determined through a “hit-or-miss” approach.
The product of the nacre gene is an acidic protein (nacrein) implicated in pearl formation. Nacrein has a calcium ion binding activity. A pearl is an aggregation of calcium carbonate, among other components, on an organic matrix.
Inefficiency in the traditional methods of cultivation is due in large part to lack of understanding of the pearl formation process at the molecular level. This lack of understanding, in turn, is due in large part to lack of access to the genetic information underlying the pearl formation process. Sequences of a limited number of genes of certain species of pearl oyster have been disclosed. See, for example, U.S. Pat. Nos. 5,968,772 and 6,001,592.
The present invention addresses these problems by providing polynucleotides and polypeptides from the nacre gene of Pinctada margaritifera. These polynucleotides and polypeptides can be used in a variety of ways, including in improved methods of pearl oyster cultivation.